JP4798408B1 - Simple determination method of low concentration manganese - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for easily and rapidly quantifying low concentration manganese present in sample water on site.
SOLUTION: An oxidizing agent anion is added to sample water to oxidize dissolved manganese species to colored permanganate ions, and then a bulky cation is added to add permanganate ions and an oxidizing agent anion. After producing a hydrophobic ion aggregate composed of three components of ions and bulky cations , the solution is passed through a filtration membrane without using naphthalene as an extraction medium. It is chemically adsorbed and collected on the surface of the filtration membrane, and the manganese concentration is determined by the degree of coloring of the filtration membrane.
[Selection] Figure 1

Description

  The present invention relates to a method for quickly and simply quantifying the concentration of dissolved manganese chemical species contained in trace amounts in environmental water such as ground water and river water, drinking water, industrial water, and the like.

  Manganese is a transition metal having an atomic number of 25, is widely distributed as a mineral in the crust, and is universally present as ions and colloids in environmental waters such as groundwater and river water. Metallic manganese (zero-valent manganese) is used as an additive during refining, manganese dioxide (tetravalent manganese) is used as a dry battery and an oxidizing agent, potassium permanganate (7-valent manganese) is a strong oxidizing agent, It is widely used in the industry, such as being used as a bleaching agent, and is rarely detected from mine wastewater or factory wastewater.

  Manganese in water is colored by oxidation even when present in a trace amount, causing so-called “black water”, and has a strange odor at higher concentrations. From the viewpoint of preventing such obstacles, for example, according to the Waterworks Law, the concentration of manganese and its compounds is set to 0.05 mg or less per liter of tap water with respect to the amount of manganese.

  In recent years, it has been pointed out that the elution of metals such as manganese is promoted by pollution and acidification of rivers and lakes. Therefore, there are concerns about the impact on waterworks, beverage production, and industrial water, and a quick and steady grasp of the manganese concentration in the water is required.

  Highly accurate instrumental analysis using atomic absorption spectrophotometry, inductively coupled plasma emission spectrometry, and inductively coupled plasma mass spectrometry (quantitative water test method, JIS K 0101, JIS) K 0102) has been established and is used for official measurements at water purification plants. These instrumental analysis methods can provide highly sensitive and highly accurate measurement values, but require expensive, large, and unusable analytical instruments, and require skill in operation. Therefore, these methods are not applicable to on-site analysis.

  In addition to the silver periodate method specified in the water test method, the formaldoxime method, the acetoaldoxime method, and the like have been proposed as an absorptiometric method using a coloring reagent. The silver potassium periodate spectrophotometric method is excellent in selectivity with respect to manganese, but has low sensitivity. Therefore, in order to measure manganese at a tap water quality standard value level, a complicated heating and concentration operation of adding an acid as a pretreatment and boiling is essential. On the other hand, other absorptiometric methods such as the formaldoxime method are excellent in sensitivity but are difficult to apply to actual samples because of poor selectivity.

  As an example of an analytical instrument suitable for on-site analysis of manganese using the principle of the silver potassium periodate method, a simple analytical instrument (pack test: registered trademark) described in Patent Document 1 is widely used. Since it is low, it is difficult to measure manganese ion concentration at tap water quality standard and environmental standard level.

The pack test (registered trademark) described above is an analytical instrument in which a reagent prepared so as to develop color in response to a specific substance (target substance) is sealed in a polyethylene tube. When using, pull out the line (plug member) sandwiched between the welds at the end of the polyethylene tube to form a through hole with the inside, crush the polyethylene tube with your fingers to push out the air inside, and drop 1.5 mL of sample water Inhale like. The sample water sucked in reacts with reagents and develops color, and the color tone depends on the concentration of the target substance. This is visually compared with a standard color sequence color-coded for each concentration after a predetermined time, and a numerical value corresponding to the closest color is read to obtain the concentration of the target substance contained in the sample water.
In the case of a pack test using manganese as a target substance, dissolved manganese chemical species are oxidized to colored permanganate ions at pH 7, normal temperature, and reaction time 30 seconds, and the concentration can be determined from the degree of color of the solution. Although this can be applied to on-site analysis, the measurement range is 0.5 to 20 mg / L and the sensitivity is low.

  When the sensitivity of the analytical method is low, high sensitivity can be achieved by combining some separation and concentration operations, and the target substance contained in the sample water at a low concentration may be quantified. As means for that purpose, for example, distillation by heating, solvent extraction, and the like can be mentioned. However, all of them are complicated and difficult to apply to on-site analysis.

  As a prior art that combines the principle of simple absorptiometry and the separation and concentration method, the colored product is collected on the surface of a filtration membrane such as a membrane filter by filtration, and then present at a low concentration due to the degree of coloration of the filter A method for determining the concentration of the target component has been proposed. For example, methods for antimony and formaldehyde have been reported (see Patent Documents 2 and 3). These methods are relatively simple and can be applied to on-site analysis, but methods for manganese have not been established so far.

Japanese Patent No. 4125603 Japanese Patent Laid-Open No. 2004-257806 JP 2007-218866 A

  The on-site analysis technology that enables measurement at a water sampling point such as a water source can be used easily without special equipment. It is useful for screening tests for grasping approximate values and for self-inspection for water. Manganese is also included in the target component, and tap water quality standard and environmental water quality standard, that is, 0.05 mg / L level is assumed as a practical concentration range.

  However, an on-site analysis technique for manganese present at a low concentration of 0.05 mg / L in sample water has not been established so far.

The object of the present invention is to convert dissolved manganese species present in sample water at the standards of tap water quality and environmental standards into colored permanganate ions by the principle of spectrophotometry using highly selective periodate. Concentrated by chemically adsorbing and collecting on the surface of the filter membrane by adding specific reagents and filtering, and simple, quick and on-site for determining manganese concentration by the degree of coloration of the filter membrane Is to provide a simple method.

As a result of intensive studies in view of the above problems, the present inventors have oxidized dissolved manganese species in sample water to colored permanganate ions with an oxidizing agent anion, and then added bulky cations to the solution. When added and passed through the filtration membrane, permanganate ions are chemically adsorbed and collected on the surface of the filtration membrane without using naphthalene as an extraction medium, and the coloring degree of the filtration membrane is roughly proportional to the dissolved manganese species concentration. I found out. The present invention has been completed based on this scientific knowledge.

The simple quantitative method of low concentration manganese of the present invention is to add an oxidizing agent anion to sample water, oxidize dissolved manganese species to colored permanganate ions, and then add bulky cations, After forming a hydrophobic ion aggregate composed of three components of permanganate ion, oxidizing agent anion and bulky cation , the solution is passed through a filtration membrane without using naphthalene as an extraction medium. The hydrophobic ion aggregate is chemically adsorbed and collected on the surface of the filtration membrane, and the manganese concentration is determined by the degree of coloring of the filtration membrane.

  According to the said structure, an oxidizing agent anion is added to sample water, a dissolved manganese chemical species is oxidized, and it converts into a colored heptavalent permanganate ion.

  Next, a bulky cation is added to the oxidized solution, and a colored hydrophobic ion aggregate of permanganate ion, which is an anion, and a bulky cation, and an oxidizing agent anion and a bulky cation. To form a hydrophobic ion aggregate. These hydrophobic ion aggregates are formed by electrically attracting permanganate ions, oxidant anions, and bulky cations. These hydrophobic ion aggregates are electrically neutral and difficult to dissolve in water. Hydrophobic ion aggregates containing permanganate ions are quantitatively incorporated into hydrophobic ion aggregates containing oxidant anions and are composed of three components: permanganate ions, oxidant anions and bulky cations. Hydrophobic ion aggregates consisting of

  The solution containing the produced hydrophobic ion aggregate is passed through the filtration membrane, and the hydrophobic ion aggregate is adsorbed and collected on the surface of the filtration membrane. Thereby, the hydrophobic ion aggregate is easily separated and concentrated from the aqueous phase. This is because the hydrophobic ion aggregate is adsorbed and collected on the surface of the filtration membrane due to the chemical affinity acting between the material of the filtration membrane and the hydrophobic ion aggregate. The surface of the filtration membrane is colored by permanganate ions contained in the adsorbed and collected hydrophobic ion aggregates.

  By determining in advance the relationship between the degree of coloring of the filtration membrane and the concentration of dissolved manganese species, the concentration of dissolved manganese species is determined by evaluating the degree of coloring of the filtration membrane.

  In the above configuration, the dissolved manganese chemical species to be quantified is a chemical species that contains manganese in its chemical structure and has the property of changing to permanganate ions by the addition of an oxidizing agent anion. It is. Specifically, a manganese chemical species having any oxidation number from monovalent to 7-valent that exists in an inorganic free ion state in the sample water is applicable.

  In the above configuration, the oxidant anion is a chemical species that has a redox potential sufficient to oxidize dissolved manganese species to permanganate ions in an aqueous solution and exists as an anion in the aqueous solution.

  In the above configuration, the bulky cation is a cation having a property of forming a hydrophobic ion aggregate with a permanganate ion and an oxidizing agent anion in an aqueous solution. The characteristics of the cation having such properties are that the hydrated ion radius is large, the structure has a hydrophobic structure such as a carbon chain, and the charge is small and delocalized in the ion. Have.

  In the above structure, the hydrophobic ion aggregate is a weakly hydrophilic compound in which an anion and a bulky cation are electrically attracted to become electrically neutral as a whole.

  Furthermore, in the simple determination method of low concentration manganese of the present invention, the bulky cation is a quaternary ammonium ion or a quaternary phosphonium ion.

  According to the said structure, an optimal thing is selected as a bulky cation.

  In the simple quantitative method for low-concentration manganese according to the present invention, the oxidizing agent anion is periodate ion, perchlorate ion or peroxodisulfate ion.

  According to the above configuration, the optimum oxidant anion is selected.

  The simple determination method of low-concentration manganese according to the present invention includes adding an oxidizing agent anion to sample water to oxidize dissolved manganese species to colored permanganate ions, and then suspending substances and / or iron content. After removing only the colored substance derived from the product by filtration, a hydrophobic ion aggregate composed of three components of permanganate ion, oxidizing agent anion, and bulky cation is generated.

  According to the above configuration, after adding an oxidizing agent anion to the sample water to oxidize the dissolved manganese chemical species into colored permanganate ions, the suspension material and / or the colored material derived from iron is derived from the sample water. In addition, suspended substances and / or colored substances derived from iron produced in the step of oxidizing the dissolved manganese chemical species to colored permanganate ions by adding an oxidizing agent anion to the sample water are removed by filtration. Subsequently, a hydrophobic ion aggregate consisting of three components of permanganate ion, oxidant anion and bulky cation is produced from the filtrate. Thereby, coloring of the filtration membrane by substances other than dissolved manganese chemical species can be prevented.

  Furthermore, the simple quantitative method for low-concentration manganese according to the present invention is the same as the filtration membrane for adsorbing and collecting hydrophobic ion aggregates in order to remove the suspended substances and / or colored substances derived from iron. It is characterized by using a filtration membrane and using the back side of the surface that adsorbs and collects hydrophobic ion aggregates.

  According to the said structure, the filtration for removing the colored substance derived from the said suspended substance and / or iron is performed using the back surface of the same filtration membrane as the filtration membrane which adsorbs and collects a hydrophobic ion aggregate. carry out. Hydrophobic ion aggregates are adsorbed and collected on the surface of the filtration membrane, and the two purposes of removing colored substances and adsorbing and collecting hydrophobic ion aggregates on the front and back of the same filtration membrane are achieved. .

  Furthermore, in the simple quantitative method for low concentration manganese of the present invention, the filtration membrane is a membrane filter.

  According to the above configuration, the hydrophobic ion aggregate is adsorbed and collected on the membrane filter.

  The simple quantitative method for low-concentration manganese according to the present invention is characterized in that the manganese concentration is determined by evaluating the degree of coloring of the filtration membrane by visual comparison with a standard color sequence prepared in advance.

  According to the said structure, the coloring degree of a filtration membrane is uniquely determined by the density | concentration of the dissolved manganese chemical species contained in sample water. The degree of coloration of the filter membrane varies depending on the concentration of dissolved manganese species. The relationship between the degree of coloration of the filtration membrane and the concentration of dissolved manganese chemical species is determined in advance, and a standard color sequence is created. Seed concentration can be determined immediately.

  The simple quantitative method for low-concentration manganese according to the present invention is characterized in that the degree of manganese concentration is determined by measuring the degree of coloring of the filtration membrane with a measuring instrument and evaluating it with a calibration curve prepared in advance.

  According to the said structure, the coloring degree of a filtration membrane is measured as a reflected light absorbency and a color difference with a measuring device, and a manganese concentration can be determined by evaluating the coloring degree of a filtration membrane with the analytical curve created beforehand.

  According to the simple determination method of low-concentration manganese of the present invention, an oxidizing agent anion and a bulky cation are sequentially added to a predetermined amount of sample water, and the solution is passed through a filtration membrane, whereby the sample water Dissolved manganese species can be collected quantitatively on the filter membrane surface, and the concentration of dissolved manganese species can be determined quickly by evaluating the degree of coloration of the filter membrane surface derived from the dissolved manganese species. can do. Since the dissolved manganese species contained in the sample water are collected on the surface of the minute filtration membrane, high sensitivity is achieved by concentration. For this reason, it is prescribed as a tap water quality standard and an environmental standard without using expensive analytical instruments such as an atomic absorption photometer, an inductively coupled plasma emission spectrometer, an inductively coupled plasma mass spectrometer, and a spectrophotometer. It is possible to measure a low concentration region such as about 05 mg / L. Furthermore, by using together with a commercially available simple analytical instrument, an instrument for adding a pre-divided reagent, an instrument for easily performing filtration, etc., even if there is no specialized knowledge or equipment, the entire operation is 3 minutes. It is possible to carry out the measurement easily and to the extent that it can be applied to on-site analysis.

  Moreover, by using a quaternary ammonium ion or a quaternary phosphonium ion as a bulky cation, a hydrophobic ion aggregate containing a permanganate ion quantitatively can be efficiently generated.

  In addition, by using periodate ion, perchlorate ion or peroxodisulfate ion as oxidant anion, the oxidation of dissolved manganese species to permanganate ion is performed quantitatively and at the same time It is possible to provide a component of a hydrophobic ion aggregate in the solution that acts as a carrier for efficiently collecting the ion.

  Furthermore, after adding an oxidizing agent anion, filtration is performed with a filtration membrane, and by adding a bulky cation to the filtrate, the coloration degree of the filtration membrane derived from dissolved manganese species in the sample water is affected. Therefore, it is possible to remove only suspended substances and / or colored substances derived from iron, and the manganese concentration can be determined with high accuracy. For this reason, it can be widely applied to environmental water such as ground water and river water, and sample water containing suspended solids and / or iron such as drinking water and industrial water.

  Further, the same filtration membrane is used for filtration for removing suspended substances and / or colored substances derived from iron in sample water and for collecting hydrophobic ion aggregates containing permanganate ions. By using each of the back surface and the front surface, removal of colored substances and collection of hydrophobic ion aggregates can be performed efficiently and quickly.

  Further, by using a membrane filter as the filtration membrane, permanganate ions existing as hydrophobic ion aggregates in the solution can be quantitatively collected on the surface of the filtration membrane without color unevenness.

  In addition, by evaluating the degree of coloration of the filtration membrane by visually comparing the standard color sequence prepared in advance with the color of the filtration membrane, the concentration of dissolved manganese species can be determined immediately without the need for any analytical equipment. be able to.

  In addition, the degree of coloration of the filter membrane is measured as a reflection absorbance or a color difference by a measuring instrument, and the degree of coloration of the filter membrane is evaluated by a calibration curve prepared in advance, so that it is not affected by the light source and is used for evaluating the degree of coloration The concentration of dissolved manganese species can be determined without receiving individual differences.

It is a flow figure showing roughly the simple quantitative method of low concentration manganese concerning the embodiment of the present invention. The relationship between the benzethonium chloride concentration in the sample water and the reflection absorbance derived from the hydrophobic ion aggregate containing the permanganate ions collected on the filter membrane is shown. The influence of pH when collecting hydrophobic ion aggregates containing permanganate ions in the filter membrane is shown. Fig. 3 shows the coloration of hydrophobic ion aggregates containing permanganate ions collected on the filter membrane by various concentrations of manganese (II) ions. The relationship figure of the reflected absorbance derived from the density | concentration of the manganese (II) ion in sample water and the hydrophobic ion aggregate containing the permanganate ion collected by the filtration membrane is shown. Using pack test (registered trademark), which is a commercially available simple analytical instrument containing an oxidant anion for oxidation of dissolved manganese chemical species, using the hot spring water as a sample and using pack test (registered trademark) The coloring of the filtration membrane when the present invention is carried out is shown. The coloring of the filtration membrane when hot spring water is measured according to the present invention is shown. The coloring of a filtration membrane when hot spring water is measured by the present invention without performing filtration for removing suspended substances and / or iron is shown.

  Hereinafter, embodiments of the present invention will be described in detail.

  As shown in FIG. 1, in the present invention, (a) a predetermined amount of oxidant anion is added to a predetermined amount of sample water, and dissolved manganese species contained in the sample water are converted into permanganate ions. Hydrophobic ion group consisting of three components: permanganate ion, oxidant anion and bulky cation by adding bulky cation to the solution obtained in the first step (b) (b) A second step of generating a coalescence, (c) a third step of collecting the ion aggregate on the surface of the filtration membrane by passing the solution obtained in (b) through the filtration membrane, and (d) prepared in advance. This is a fourth step in which the manganese concentration is determined by evaluating the degree of coloring of the filtration membrane obtained in (c) by visual comparison with a standard color or measurement of reflection absorbance.

  The sample water to be used in the present invention is assumed to be tap water, raw water for drinking, or industrial water that is likely to be affected by coloring, and therefore exhibits high accuracy in the vicinity of a tap water quality standard of 0.05 mg / L. The amount of sample water used for measurement can be set so that each reagent can be added, and the amount of each reagent added is determined according to the amount of sample water. As the amount of sample water increases, the concentration factor can be increased, and a lower concentration of manganese can be measured. Although there is no restriction | limiting in the concrete numerical value, 1 mL-100 mL are desirable from a viewpoint of reducing the time which filtration requires, and the amount of required reagents, and simplifying.

  The dissolved manganese species to be quantified are manganese species with any oxidation number from 1 to 7 that exist in the sample water in an inorganic free ion state. When manganese existing as a form is targeted, it can be quantified after performing dissolution treatment as necessary to obtain dissolved manganese species.

(A) First step First, an oxidant anion is added to a predetermined amount of sample water. By this step, dissolved manganese species in the sample water are oxidized and converted to permanganate ions having a reddish purple color. The analytical chemical application of this chemical reaction is a conventional technique, including the silver potassium periodate absorptiometry in the above-mentioned water supply test method, the industrial water test method (JIS K 0101) and the factory waste water test method (JIS K 0102). ) Etc. are widely used. In this step, a commercially available simple analytical instrument containing an oxidizing agent anion to which the above test method or the above test method is applied can be used.

  As an oxidizing agent anion, periodate ion, perchlorate ion, peracetic acid ion, pernitrate ion, perborate ion, perbromate ion or peroxodisulfate ion (persulfate ion), which are strong oxidants, are used. Can be used. Although not particularly limited, potassium periodate is desirable as a reagent to be added.

  The oxidant anion is necessary not only to act as an oxidant that changes dissolved manganese species to permanganate ions, but also to generate hydrophobic ion aggregates that can be collected by filtration membranes. In comparison with the dissolved manganese species that are the target substances, a large excess is required. When using potassium periodate, it is desirable to add so that the potassium periodate concentration in the sample water is 1 mM to 10 mM.

  In this first step, a reaction time is required for the dissolved manganese species in the sample water to be converted quantitatively into permanganate ions. This reaction time varies depending on the kind of the oxidant anion, the temperature of the solution, and the pH, but can be completed within a few minutes by acidification of the sample solution or combined use of the catalyst. The term “quantitative” as used herein does not necessarily mean that the reaction is 100% complete. If a reproducible result can be obtained, it is possible to place importance on quickness without waiting for completion of the reaction.

(B) Second step Next, a bulky cation is added to the solution obtained in the first step. By this step, a hydrophobic ion aggregate composed of three components of permanganate ion, oxidizing agent anion and bulky cation is generated. This step is necessary to collect permanganate ions in the filtration membrane in the third step described later.

  When a bulky cation is added to the solution that has completed the first step, a colored hydrophobic ion aggregate of a permanganate ion, which is an anion present in a low concentration in the solution, and a bulky cation is formed. . On the other hand, bulky cations that have not reacted with permanganate ions produce a large amount of hydrophobic anion and oxidant anion added in large excess in the first step, resulting in white turbidity. . Since the amount of the colored ion aggregates containing the permanganate ion in the former depends on the dissolved manganese species concentration in the sample water, it is very small but highly hydrophobic. Therefore, it is quantitatively taken into the cloudiness of the hydrophobic ion aggregate containing the latter oxidizing agent anion.

  Hydrophobic ion aggregates that have incorporated permanganate ions quantitatively are electrically neutral and are difficult to dissolve in water. Therefore, since it is easily adsorbed and collected on the filtration membrane surface by the filtration operation in the third step, it can be easily separated and concentrated from the aqueous phase.

  As the bulky cation, a quaternary ammonium ion, a quaternary phosphonium ion, or a positively charged amine having a certain number of carbon atoms and having a hydrophobic site in the molecule can be used. The reagent to be added is not particularly limited, and examples thereof include benzethonium chloride, benzyldimethyltetradecylammonium chloride, benzalkonium chloride, cetylpyridinium chloride, and the like, and benzethonium chloride and benzyldimethyltetradecylammonium chloride are preferably used.

  In this second step, when no bulky cation is added, permanganate ions are hardly adsorbed on the filtration membrane. In addition, if the amount of bulky cation added is too large, clogging is likely to occur during filtration in the third step, and all of the generated hydrophobic ion aggregates are not retained on the filtration membrane, and partly Flows into the filtrate. Therefore, there is an appropriate range for the amount of bulky cation added, and there is no particular limitation. However, when benzethonium chloride is used, it is added so that the benzethonium chloride concentration in the sample solution is 0.3 mM to 3 mM. It is desirable to do. Alternatively, benzethonium chloride is preferably added in a molar ratio of 0.1 to 1 with respect to potassium periodate. FIG. 2 shows the reflection absorbance of the hydrophobic ion aggregates collected on the filter membrane surface when the benzethonium chloride concentration was changed. The value of reflection absorbance is derived from permanganate ions collected as hydrophobic ion aggregates.

  In this second step, the reaction for forming the hydrophobic ion aggregate is completed quickly in about several seconds.

  In the second step, the pH of the solution at the time of forming the ion aggregate is desirably 7 or less. FIG. 3 shows the reflection absorbance of ion aggregates collected on the filtration membrane when the pH is changed.

(C) Third step Subsequently, the solution obtained in the second step is passed through a filtration membrane. By this step, hydrophobic ion aggregates containing permanganate ions are adsorbed and collected on the surface of the filtration membrane.

  Filter membranes include membrane filters (microfiltration membranes), filter paper, solid phase extraction columns filled with solid phase extractants, polyethylene sintered filters, nonwoven fabrics, synthetic fiber networks (nylon mesh, etc.), and the like. Although not particularly limited, a membrane filter is desirable for collecting ion aggregates without color unevenness.

  Examples of the material for the membrane filter include cellulose mixed ester, cellulose acetate, polytetrafluoroethylene, polyethersulfone, and nylon. Although not particularly limited, cellulose mixed esters and nylon exhibiting strong affinity with hydrophobic ion aggregates are desirable.

  As a method of passing a solution containing hydrophobic ion aggregates through the filtration membrane, select a method that suits the purpose of use, such as vacuum filtration, pressure filtration, gravity filtration, etc. used in general filtration. can do. Similarly, the instrument required for this is not particularly limited as long as the degree of coloration of the filtration membrane can be observed, but a small filtration instrument loaded with a filtration membrane or a separable filter unit that can be easily attached to and detached from a syringe. Filter holders and syringe filters are recommended.

  The small filtration device loaded with the above-mentioned filtration membrane has a filtration membrane loaded in the opening portion of the wide mouth, and is exposed so that the surface of the filtration membrane can be seen directly from the opening portion, and the opposite side of the opening portion is hollow. A conical portion is provided. A sintered body for supporting the filtration membrane is provided between the opening and the cone. Further, a guide member for connecting the opening and the syringe is provided.

  The effective filtration area of the filtration membrane is not particularly limited, but it affects the degree of coloration of the filtration membrane after the collection of the hydrophobic ion aggregates, so it is necessary to set a predetermined value. When conditions such as the amount of sample water and the concentration of dissolved manganese species are constant, the degree of coloration of the filtration membrane and the effective filtration area are generally inversely related. Accordingly, when the effective filtration area is set to be small, the sensitivity is increased, so that a lower concentration of manganese can be measured. The effective filtration area is preferably 0.1 cm2 to 20 cm2.

(2) Fourth Step Finally, the degree of coloration of the filtration membrane obtained in the third step is evaluated.
The evaluation of the degree of coloring of the filtration membrane can be carried out by visually comparing the color of the filtration membrane and the standard color sequence. The degree of coloring is evaluated by visually comparing the color of the filter membrane and the standard color sequence, and the manganese concentration is determined. The standard color sequence is a step-by-step presentation of the concentration of dissolved manganese species in the measurement range and the corresponding color. By selecting the color most similar to the color of the filtration membrane, the measurer selects the concentration. The determination can be performed very simply.

  Alternatively, the degree of coloration on the surface of the filtration membrane is measured with a measuring instrument as reflected absorbance or color difference, and the manganese concentration is determined by a calibration curve prepared in advance. The degree of coloration on the surface of the filtration membrane can be measured with a measuring instrument such as a reflectometer, a color difference meter, a spectrocolorimeter, a densitometer, and a TLC scanner.

  The coloring degree of the filtration membrane is constant for at least about 30 minutes, but fading occurs gradually when left for a long time. If the degree of coloring of the filtration membrane changes, it will affect the determination of manganese concentration, so it is desirable to move to the fourth step as soon as possible after the third step is completed.

  When the sample water contains a large amount of suspended matter and / or iron, the coloring matter derived from them is collected on the surface of the filtration membrane, affecting the coloring degree derived from manganese, and determining the manganese concentration. It can be difficult.

  In such a case, filtration is performed using a filtration membrane when the first step is completed, and then the second step and subsequent steps are applied to the filtrate to remove suspended substances and / or colored substances derived from iron. can do. According to the present invention, it is possible to remove only the colored substance derived from the suspended substance and / or iron without affecting the coloring degree derived from manganese, and the determination of the manganese concentration can be performed with high accuracy. This is an effective method for the sample water containing a large amount of suspended matter and / or iron as described above.

  The filtration for removing the colored substance derived from the suspended substance and / or iron must be performed using a filtration membrane different from the filtration membrane used in the third step or a different filtration surface. Moreover, in order to work simply and quickly, it is preferable to perform the filtration and the filtration for adsorbing and collecting the hydrophobic ion aggregate on the back surface and the surface of the same filter membrane, respectively.

<When the first step is performed based on JIS K 0102>
Take 10 mL of sample water containing manganese (II) ions in a glass beaker, add 0.3 mL of 1 M sulfuric acid and 10 mg of potassium periodate, and boil for about 10 minutes to generate permanganate ions. .
1.5 mL of a solution in which permanganate ions were generated was placed in another container, and 50 μL of 40 mM benzethonium chloride aqueous solution was added thereto to generate hydrophobic ion aggregates containing permanganate ions. The solution was cloudy.
The clouded solution was sucked up with a syringe, and a small filtration device (effective filtration area 12 mm 2, pore size 1.2 μm) loaded with a nylon membrane filter was connected to the syringe into which the solution was sucked by an induction member, and the solution was allowed to pass through.
Hydrophobic ion aggregates containing permanganate ions were collected on the membrane filter surface, and the surface of the membrane filter was uniformly colored purple-red without color unevenness. FIG. 4 shows the coloration of the filtration membrane surface when sample water having manganese (II) ion concentrations of 0, 0.02, 0.05, 0.1 and 0.2 mg / L was measured according to the present invention.
Further, the reflection absorbance at 520 nm on the surface of the membrane filter was measured with a spectrocolorimeter (product name: CM-2600d, manufactured by Konica Minolta Co., Ltd.), and the degree of reddish purple coloring was evaluated. FIG. 5 shows the results of measuring sample water with manganese (II) ion concentrations of 0, 0.02, 0.05, 0.1, 0.2, 0.5, and 1 mg / L according to the present invention.

<When the first process is performed by Pack Test (registered trademark)>
Sample water containing manganese (II) ion is sucked into a polyethylene tube of pack test (product name: pack test manganese, manufactured by Kyoritsu Riken Co., Ltd.), and permanganic acid at pH 7, normal temperature, and reaction time 30 seconds. After the ions were generated, the entire solution was extruded from the polyethylene tube into another container.
50 μL of 50 mM benzethonium chloride was dropped into the opening of a small filtration device (effective filtration area 12 mm 2, pore diameter 1.2 μm) loaded with a nylon membrane filter and impregnated on the surface side of the filter. Connect the small filtration device and the syringe with a guide member, immerse the tip of the cone of the small filtration device in the solution in the container, and pull up the plunger to pass the solution from the back side of the membrane filter to the front side. I let you. As the solution passed through the membrane filter, a hydrophobic ion aggregate containing benzethonium ions and permanganate ions was formed, and the solution became cloudy in the syringe.
Subsequently, the plunger of the syringe was pushed back to pass the cloudy solution from the front surface side to the back surface side of the membrane filter. The syringe and the guide member were removed from the membrane filter through which the solution was passed, and the standard color was compared with the red-purple coloring of the hydrophobic ion aggregates containing permanganate ions collected on the membrane filter surface.
As a result, 0.02 mg / L or more of manganese ions could be detected, and determinations of 0.02, 0.05, 0.1, 0.2, 0.5, and 1 mg / L could be made. .
The measurement range of the pack test for manganese ions is 0.5, 1, 2, 5, 10, and 20 mg / L. When the manganese ion concentration is less than 0.5 mg / L, the color is light and the concentration is determined in the pack test. Although it cannot be confirmed, the sensitivity increased about 20 times by carrying out the present invention.

<Application to hot spring water>
As an application to an actual sample, the operation described in Example 2 was applied to hot spring water. That is, 1.5 mL of hot spring water containing a large amount of suspended solids and iron and exhibiting brown color was sucked into a polyethylene tube for pack test, and permanganate ions were generated at pH 7, normal temperature, and reaction time 30 seconds. Later, the entire solution was extruded from the polyethylene tube into another container.
50 μL of 50 mM benzethonium chloride was dropped into the opening of a small filtration device (effective filtration area 12 mm 2, pore diameter 1.2 μm) previously loaded with a nylon membrane filter and impregnated on the surface side of the filter. Connect the small filtration device and the syringe with a guiding member, immerse the tip of the cone of the small filtration device in the solution put out in the container, and pull up the plunger of the syringe, from the back side to the front side of the membrane filter The solution was passed through. As the solution passed through the membrane filter, a hydrophobic ion aggregate containing benzethonium ions and permanganate ions was formed and became cloudy in the syringe. At this time, the suspended matter contained in the sample water and the colored substance derived from the iron were captured on the back side of the sintered body and the membrane filter provided in the small filtration device. Subsequently, the plunger of the syringe was pushed back to pass the cloudy solution from the front surface side to the back surface side of the membrane filter.
The syringe and the guide member were removed from the membrane filter through which the solution was passed, and the magenta color on the surface of the membrane filter was compared with the standard color sequence. As a result, it was determined that the manganese ion in the hot spring water was about 1 mg / L.
Figure 6 shows the color development in the polyethylene tube of the pack test when using hot spring water as a sample, and the pack test is used in the first step to collect the hydrophobic ion aggregates in the nylon membrane filter. It compares the coloring after being made, and shows that the darkness of the color has increased by about 20 times by applying a concentration operation with a membrane filter.
FIG. 7 shows a state in which the manganese concentration is obtained by comparing the coloration of the membrane filter surface with a standard color sequence prepared in advance for the degree of coloration of the membrane filter when hot spring water is targeted.

In order to evaluate the effect of removing suspended solids and / or colored substances derived from iron by performing filtration using a filtration membrane when the first step is completed, the operation described in Example 3 is performed as a comparison in the first step. This was done in a manner that did not require subsequent filtration.
That is, 1.5 mL of hot spring water was sucked into a polyethylene tube for pack test to generate permanganate ions at pH 7, normal temperature, and reaction time 30 seconds, and then the entire amount of the solution was extruded from the polyethylene tube into another container. 50 μL of 50 mM benzethonium chloride aqueous solution was added to the solution pushed out to another container to produce a hydrophobic ion aggregate containing permanganate ions. This solution was cloudy.
The white turbid solution is sucked up with a syringe, a small filtration device (effective filtration area 12 mm2, pore size 1.2 μm) loaded with a nylon membrane filter and the syringe into which the solution is sucked are connected by a guide member, and the solution is placed on the surface side of the membrane filter. From the back side.
The surface of the membrane filter is colored orange due to suspended matter and iron contained in hot spring water, in addition to the reddish purple color derived from permanganate ions, resulting in a coloration different from the standard color sequence and a colorimetric comparison with the standard color sequence It was difficult. Fig. 8 shows a state where the hot spring water-derived suspension and iron were collected and colored on the surface of the membrane filter, and the color was different from the standard color sequence created in advance. ing.

  The present invention is not limited to the above-described embodiments or examples, and the technical scope includes conditions within the scope not departing from the gist of the invention described in the claims.

Claims (8)

Add oxidant anion to sample water to oxidize dissolved manganese species to colored permanganate ion, then add bulky cation, permanganate ion, oxidant anion and bulky After the formation of a hydrophobic ion aggregate composed of three cationic components , the solution is passed through the filtration membrane without using naphthalene as an extraction medium , and the hydrophobic ion aggregate is removed from the surface of the filtration membrane. A simple method for quantitative determination of low-concentration manganese, characterized in that it is chemically adsorbed and collected and the manganese concentration is determined by the degree of coloration of the filtration membrane. The simple quantitative method for low-concentration manganese according to claim 1 , wherein the bulky cation is a quaternary ammonium ion or a quaternary phosphonium ion.   The simple quantification method for low-concentration manganese according to claim 1 or 2, wherein the oxidant anion is periodate ion, perchlorate ion or peroxodisulfate ion.   After adding an oxidizing agent anion to the sample water to oxidize the dissolved manganese species to colored permanganate ions, only the suspended matter and / or colored matter derived from iron is removed by filtration, The simple determination method of low concentration manganese according to any one of claims 1 to 3, wherein a hydrophobic ion aggregate comprising three components of a permanganate ion, an oxidizing agent anion, and a bulky cation is generated.   The filtration for removing colored substances derived from the suspended substances and / or iron is used in the same filtration membrane as that for absorbing and collecting hydrophobic ion aggregates, and adsorbs hydrophobic ion aggregates. It implements using the back surface side of the surface to collect, The simple determination method of the low concentration manganese of Claim 4 characterized by the above-mentioned.   The simple filtration method for low-concentration manganese according to any one of claims 1 to 5, wherein the filtration membrane is a membrane filter.   The low concentration manganese according to any one of claims 1 to 6, wherein the manganese concentration is determined by evaluating the coloring degree of the filtration membrane by visual comparison with a standard color sequence prepared in advance. Simple quantitative method.   The concentration of manganese in the low-concentration manganese according to any one of claims 1 to 6, wherein the concentration of manganese is determined by measuring the degree of coloring of the filtration membrane with a measuring instrument and evaluating it with a calibration curve prepared in advance. Simple quantitative method.

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